With the caveat that the new regulations are coming into effect right now (or tomorrow, or next week or month, or something). Some people have been told by officials that under the new rules, people will have to get their visa before coming to Mexico, but I just think it unlikely that they can make that work.

What you need to do in advance is to have your qualifications Apostilled in your home country or legalized if you are from a country that is not party to Hague Convention which established the Apostille process.

What's your background? Are you interested in a specific part of Mexico?

I agree with the usual advice of showing up then seeking a job, but if you are looking for an international school job, there are some job fairs in the US you could try first for a hire. January is the month for such fairs and several Mexican schools are usually represented.